The present invention relates to a pouch for sealingly containing retort food which is easily tearable for discharging the food.
A laminate sheet is conventionally used as a material of a pouch for containing a retort food. The laminate sheet includes a laminate film formed of plastic material layers, and an aluminum foil joined or deposited thereto for enhancing breakage strength and moisture-blocking function. The laminate film has a base substrate formed of a material selected from the group consisting of polypropylene, nylon and polyester, and the film is biaxially oriented film.
Generally, a rectangular laminate sheet is folded into two sections in order to define front and rear walls, and confronting three side edge portions are heat sealed together to obtain a bag shape. Such pouch is ordinarily referred to as a "pillow type" pouch. Alternatively, two identical rectangular laminate sheets are prepared serving as the front and rear walls, and these are superposed together, and are joined at four side edge portions.
The laminate sheet of this type has high breaking strength, and therefore, it would be rather difficult to tear the pouch at the heat sealed portion so as to discharge a content packed therein. To overcome this problem, V-shaped or I-shaped notch is formed at at least one heat sealed portion in order to facilitate the tearing.
Still however, since the laminate sheet has sufficient breaking strength, it would be still difficult to align the tearing locus at the front wall with the tearing locus at the rear wall, even if tearing is initiated from the V-shaped or I-shaped notch. After tearing the pouch at the heat sealed zone, the tearing locus at a front wall of the pouch would be different from the tearing locus at the rear wall thereof. As a result, food or content may be disadvantageously flooded from the tearing opening. For example, if user only draw his attention to the front tearing line, the content may be leaked out of the rear tearing line, if the rear line is not coincident with the front line, but is positioned lower than the front line.
Another proposal has been made to overcome the above described drawback. According to the proposal, a base substrate film which also functions as heat sealing layer formed of non-oriented polypropylene is formed over an aluminum film, and linear slits are formed at the base substrate film so as to facilitate tearing. However, it would be rather difficult to align a slit at the front wall of the pouch will a slit at the rear wall thereof, and resultant pouch does not provide sufficient impact strength. Further, the aluminum foil may be directly contacted with the content which will pass through the slits of the heat sealing layer, and therefore, corrosion may occur in the aluminum foil.